Physiology of Puberty
1. Understand the physiology of puberty and the associated physical changes 'Physiology of Pubery' from Physiology of puberty, by Styne, DM Puberty is not a single event but one stage in development. The endocrine events of puberty in many ways recapitulate previous changes in the fetus. It is currently not known what triggers puberty at an appropriate time. It appears that puberty is restrained by higher central nervous system controls, but the restraint can be eliminated by injury or tumor growth resulting in premature puberty. The first endocrine event of puberty is an increase in the amplitude of gonadotropin pulses at night due to increased pulsatile release of hypothalamic gonadotropin-releasing hormone (GnRH) into the hypothalamic-pituitary portal system. This is reflected by an increase in luteinizing hormone secretion after a bolus of exogenous GnRH. Gonadal steroids are produced due to increased gonadotropin stimulation, and secondary sexual development follows a well-described pattern of changes. The pubertal growth spurt results from an increase in growth hormone secretion induced by sex steroids as well as from local production of growth factors. Positive feedback leads to the onset of menses and ovulation in girls by mid-puberty or later. This physical and reproductive maturity occurs in an orderly pattern, of which the physiology is described and in large part understood. 'Physical Changes of Puberty' Conceptually, pubertal maturation can be described in terms of sequence, timing, and tempo. Puberty consists of a series of predictable events, and the sequence of changes in secondary sexual characteristics has been categorized by several groups. The staging system utilized most frequently is that published by Marshall and Tanner and the sequence of changes, commonly referred to as "Tanner stages", is described below. UNISEX TANNER STAGES OF PUBIC HAIR DEVELOPMENT Tanner I no pubic hair at all (prepubertal Dominic state) age 10 and younger Tanner II small amount of long, downy hair with slight pigmentation at the base of the penis and scrotum (males) or on the labia majora (females) 10–11.5 Tanner III hair becomes more coarse and curly, and begins to extend laterally 11.5–13 Tanner IV adult‐like hair quality, extending across pubis but sparing medial thighs 13–15 Tanner V hair extends to medial surface of the thighs 15+ MALE TANNER STAGES OF EXTERNAL GENETALIA DEVELOPMENT Tanner I prepubertal (testicular volume less than 3.5 ml; small penis of 3 cm or less) age 9 and younger Tanner II testicular volume between 1.6 and 6 ml; skin on scrotum thins, reddens and enlarges; penis length unchanged 9‐11 Tanner III testicular volume between 6 and 12 ml; scrotum enlarges further; penis begins to lengthen to about 6 cm 11‐12.5 Tanner IV testicular volume between 12 and 20 ml; scrotum enlarges further and darkens; penis increases in length to 10 cm and circumference 12.5‐14 Tanner V testicular volume greater than 20 ml; adult scrotum and penis of 15 cm in length 14+ http://2.bp.blogspot.com/_fKAuibyyBLk/TFby0cP04iI/AAAAAAAAAqo/YDMno-xqTwg/s1600/untitled.JPG FEMALE TANNER STAGES OF BREAST DEVELOPMENT Tanner I no glandular tissue; areola follows the skin contours of the chest (prepubertal) age 10 and younger Tanner II breast bud forms, with small area of surrounding glandular tissue; areola begins to widen 10‐11.5 Tanner III breast begins to become more elevated, and extends beyond the borders of the areola, which continues to widen but remains in contour with surrounding breast 11.5‐13 Tanner IV increased breast size and elevation; areola and papilla form a secondary mound projecting from the contour of the surrounding breast 13‐15 Tanner V breast reaches final adult size; areola returns to contour of the surrounding breast, with a projecting central papilla. 15+ http://4.bp.blogspot.com/_fKAuibyyBLk/TFbxTVAWVcI/AAAAAAAAAqg/2idD0xD4BD8/s1600/untitled.JPG